Method and apparatus for transceiving control information in a wireless communication system

ABSTRACT

An embodiment of the present invention relates to a method in which a terminal receives control information in a wireless communication system, said method comprising: a step of performing blind decoding in at least one portion of a resource region except the time unit indicated by a physical control format indicator channel (PCFICH) on a subframe, said at least one portion of the resource region is determined by whether a synchronizing signal or system information is transmitted or not.

TECHNICAL FIELD

The present invention relates to a method and apparatus for transceivingcontrol information in a wireless communication system.

BACKGROUND ART

Wireless communication systems have been widely used to provide variouskinds of communication services such as voice or data services.Generally, a wireless communication system is a multiple access systemthat can communicate with multiple users by sharing available systemresources (bandwidth, transmission (Tx) power, and the like). A varietyof multiple access systems can be used. For example, a Code DivisionMultiple Access (CDMA) system, a Frequency Division Multiple Access(FDMA) system, a Time Division Multiple Access (TDMA) system, anOrthogonal Frequency Division Multiple Access (OFDMA) system, a SingleCarrier Frequency-Division Multiple Access (SC-FDMA) system, aMulti-Carrier Frequency Division Multiple Access (MC-FDMA) system, andthe like.

DISCLOSURE Technical Problem

An object of the present invention is to provide a method and apparatusfor transceiving control information, and more particularly to therelationship between e-PDCCH and a resource region to which systeminformation is transmitted during e-PDCCH transmission.

It is to be understood that technical objects to be achieved by thepresent invention are not limited to the aforementioned technicalobjects and other technical objects which are not mentioned herein willbe apparent from the following description to one of ordinary skill inthe art to which the present invention pertains.

Technical Solution

The object of the present invention can be achieved by providing amethod for receiving control information of a user equipment (UE) in awireless communication system including: performing blind decoding forthe control information in a part of a resource region other than a timeunit indicated by a physical control format indicator channel (PCFICH)on a subframe, wherein the a part of the resource region is decidedaccording to whether or not a synchronous signal or system informationis transmitted.

In a second technical aspect of the present invention, a method fortransmitting control information of a base station (BS) in a wirelesscommunication system includes: transmitting downlink control informationin a part of a resource region other than a time unit indicated by aphysical control format indicator channel (PCFICH) on a subframe,wherein the a part of the resource region is decided according towhether or not a synchronous signal or system information istransmitted.

In a third technical aspect of the present invention, a user equipment(UE) device for use in a wireless communication system includes: atransmission (Tx) module; and a processor, wherein the processorperforms blind decoding for the control information in the part of aresource region other than a time unit indicated by a physical controlformat indicator channel (PCFICH) on a subframe, wherein the the part ofthe resource region is decided according to whether or not a synchronoussignal or system information is transmitted.

In a fourth technical aspect of the present invention, a base station(BS) device for use in a wireless communication system includes: areception (Rx) module; and a processor, wherein the processor transmitsdownlink control information in the part of a resource region other thana time unit indicated by a physical control format indicator channel(PCFICH) on a subframe, wherein the the part of the resource region isdecided according to whether or not a synchronous signal or systeminformation is transmitted.

The first to fourth technical aspects may include all or some parts ofthe following items.

If the subframe may be used as a specific subframe to which at least oneof the synchronous signal and the system information is transmitted, afrequency domain to which the synchronous signal or the systeminformation is transmitted is not contained in the part of the resourceregion.

The synchronous signal may include a primary synchronous signal and asecondary synchronous signal, and the system information may betransmitted on a physical broadcast channel (PBCH).

The frequency domain may correspond to 6 resource blocks (6 RBs) locatedat a center part of an entire frequency bandwidth.

A resource region to which a reference signal is transmitted may not becontained in the part of the resource region. The reference signal (RS)may be any one of a cell-specific reference signal (RS) or channelstatus information reference signal (CSI-RS).

Advantageous Effects

As is apparent from the above description, the embodiments of thepresent invention can prevent the occurrence of collision betweene-PDCCH and a specific region to which system information istransmitted.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present invention are not limited to whathas been particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 exemplarily shows a downlink radio frame structure.

FIG. 2 exemplarily shows a resource grid of one downlink slot.

FIG. 3 exemplarily shows a downlink subframe structure.

FIG. 4 exemplarily shows an uplink subframe structure.

FIGS. 5 and 6 illustrate a resource element group (REG) serving as anallocation unit of downlink control channels.

FIG. 7 is a conceptual diagram illustrating a Physical Control FormatIndicator Channel (PCFICH) transmission scheme.

FIG. 8 shows the positions of a PCFICH and a Physical hybrid ARQindicator Channel (PHICH).

FIG. 9 shows a downlink resource element position mapped to a PHICHgroup.

FIG. 10 is a conceptual diagram illustrating a search space at eachaggregation level.

FIG. 11 is a conceptual diagram illustrating a cell-specific referencesignal.

FIG. 12 is a conceptual diagram illustrating a synchronous signal foruse in cell search.

FIG. 13 is a conceptual diagram illustrating a physical broadcastchannel (PBCH).

FIG. 14 shows transmit (Tx) time points of a synchronous signal and a

PBCH.

FIGS. 15 and 16 are conceptual diagrams illustrating an e-PDCCHallocation method and UE operations according to one embodiment of thepresent invention.

FIG. 17 is a block diagram illustrating a BS (or eNB) device and a UEdevice according to the embodiments.

BEST MODE

The following embodiments are proposed by combining constituentcomponents and characteristics of the present invention according to apredetermined format. The individual constituent components orcharacteristics should be considered optional factors on the conditionthat there is no additional remark. If required, the individualconstituent components or characteristics may not be combined with othercomponents or characteristics. Also, some constituent components and/orcharacteristics may be combined to implement the embodiments of thepresent invention. The order of operations to be disclosed in theembodiments of the present invention may be changed. Some components orcharacteristics of any embodiment may also be included in otherembodiments, or may be replaced with those of the other embodiments asnecessary.

The embodiments of the present invention are disclosed on the basis of adata communication relationship between a base station and a terminal.In this case, the base station is used as a terminal node of a networkvia which the base station can directly communicate with the terminal.Specific operations to be conducted by the base station in the presentinvention may also be conducted by an upper node of the base station asnecessary.

In other words, it will be obvious to those skilled in the art thatvarious operations for enabling the base station to communicate with theterminal in a network composed of several network nodes including thebase station will be conducted by the base station or other networknodes other than the base station. The term “Base Station (BS)” may bereplaced with a fixed station, Node-B, eNode-B (eNB), or an access pointas necessary. The term “relay” may be replaced with the terms Relay Node(RN) or Relay Station (RS). The term “terminal” may also be replacedwith a User Equipment (UE), a Mobile Station (MS), a Mobile SubscriberStation (MSS) or a Subscriber Station (SS) as necessary.

It should be noted that specific terms disclosed in the presentinvention are proposed for convenience of description and betterunderstanding of the present invention, and the use of these specificterms may be changed to other formats within the technical scope orspirit of the present invention.

In some instances, well-known structures and devices are omitted inorder to avoid obscuring the concepts of the present invention andimportant functions of the structures and devices are shown in blockdiagram form. The same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Exemplary embodiments of the present invention are supported by standarddocuments disclosed for at least one of wireless access systemsincluding an Institute of Electrical and Electronics Engineers (IEEE)802 system, a 3^(rd) Generation Partnership Project (3GPP) system, a3GPP Long Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system,and a 3GPP2 system. In particular, steps or parts, which are notdescribed to clearly reveal the technical idea of the present invention,in the embodiments of the present invention may be supported by theabove documents. All terminology used herein may be supported by atleast one of the above-mentioned documents.

The following embodiments of the present invention can be applied to avariety of wireless access technologies, for example, CDMA (CodeDivision Multiple Access), FDMA (Frequency Division Multiple Access),TDMA (Time Division Multiple Access), OFDMA (Orthogonal FrequencyDivision Multiple Access), SC-FDMA (Single Carrier Frequency DivisionMultiple Access), and the like. CDMA may be embodied through wireless(or radio) technology such as UTRA (Universal Terrestrial Radio Access)or CDMA2000. TDMA may be embodied through wireless (or radio) technologysuch as GSM (Global System for Mobile communication)/GPRS (GeneralPacket Radio Service)/EDGE (Enhanced Data Rates for GSM Evolution).OFDMA may be embodied through wireless (or radio) technology such asInstitute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi),IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (Evolved UTRA). UTRA is apart of UMTS (Universal Mobile Telecommunications System). 3GPP (3rdGeneration Partnership Project) LTE (long term evolution) is a part ofE-UMTS (Evolved UMTS), which uses E-UTRA. 3GPP LTE employs OFDMA indownlink and employs SC-FDMA in uplink. LTE-Advanced (LTE-A) is anevolved version of 3GPP LTE. WiMAX can be explained by IEEE 802.16e(WirelessMAN-OFDMA Reference System) and advanced IEEE 802.16m(WirelessMAN-OFDMA Advanced System). For clarity, the followingdescription focuses on IEEE 802.11 systems. However, technical featuresof the present invention are not limited thereto.

FIG. 1 exemplarily shows a radio frame structure for use in the LTEsystem. Referring to FIG. 1(a), a radio frame includes 10 subframes, andone subframe includes two slots in the time domain. A time required fortransmitting one subframe is defined as a Transmission Time Interval(TTI). For example, one subframe may have a length of 1 ms and one slotmay have a length of 0.5 ms. One slot may include a plurality of OFDMsymbols in time domain. Since the LTE system uses OFDMA in downlink, theOFDM symbol indicates one symbol duration. One OFDM symbol may be calledan SC-FDMA symbol or a symbol duration. An RB is a resource allocationunit and includes a plurality of contiguous subcarriers in one slot. Thestructure of the radio frame is only exemplary. Accordingly, the numberof subframes included in one radio frame, the number of slots includedin one subframe, or the number of OFDM symbols included in one slot maybe changed in various manners.

The structure of a type 2 radio frame is shown in FIG. 1(b). The type 2radio frame includes two half-frames, each of which is made up of fivesubframes, a downlink pilot time slot (DwPTS), a guard period (GP), andan uplink pilot time slot (UpPTS), in which one subframe consists of twoslots. That is, one subframe is composed of two slots irrespective ofthe radio frame type. DwPTS is used to perform initial cell search,synchronization, or channel estimation. UpPTS is used to perform channelestimation of a base station and uplink transmission synchronization ofa user equipment (UE). The guard interval (GP) is located between anuplink and a downlink so as to remove interference generated in theuplink due to multi-path delay of a downlink signal.

The structure of the radio frame is only exemplary. Accordingly, thenumber of subframes included in the radio frame, the number of slotsincluded in the subframe or the number of symbols included in the slotmay be changed in various manners.

FIG. 2 is a diagram showing a resource grid in a downlink slot. Althoughone downlink slot includes seven OFDM symbols in a time domain and oneRB includes 12 subcarriers in a frequency domain in the figure, thescope or spirit of the present invention is not limited thereto. Forexample, in case of a normal Cyclic Prefix (CP), one slot includes 7OFDM symbols. However, in case of an extended CP, one slot may include 6OFDM symbols. Each element on the resource grid is referred to as aresource element. One RB includes 12×7 resource elements. The numberN^(DL) of RBs included in the downlink slot is determined based ondownlink transmission bandwidth. The structure of the uplink slot may beequal to the structure of the downlink slot.

FIG. 3 is a diagram showing the structure of a downlink subframe. Amaximum of three OFDM symbols of a front portion of a first slot withinone subframe corresponds to a control region to which a control channelis allocated. The remaining OFDM symbols correspond to a data region towhich a Physical Downlink Shared Channel (PDSCH) is allocated. The basicunit of transmission becomes one subframe. Examples of the downlinkcontrol channels used in the 3GPP LTE system include, for example, aPhysical Control Format Indicator Channel (PCFICH), a Physical DownlinkControl Channel (PDCCH), a Physical Hybrid automatic repeat requestIndicator Channel (PHICH), etc.

PCFICH is transmitted at a first OFDM symbol of a subframe, and includesinformation about the number of OFDM symbols used to transmit thecontrol channel in the subframe.

PHICH includes a HARQ ACK/NACK signal as a response to uplinktransmission.

The control information transmitted through the PDCCH is referred to asDownlink Control Information (DCI). The DCI includes uplink or downlinkscheduling information or an uplink transmit power control command for acertain UE group. The PDCCH may include resource allocation andtransmission format of a Downlink Shared Channel (DL-SCH), resourceallocation information of an Uplink Shared Channel (UL-SCH), paginginformation of a Paging Channel (PCH), system information on the DL-SCH,resource allocation of a higher layer control message such as a RandomAccess Response (RAR) transmitted on the PDSCH, a set of transmit powercontrol commands for individual UEs in a certain UE group, transmitpower control information, activation of Voice over IP (VoIP), etc. Aplurality of PDCCHs may be transmitted within the control region. The UEmay monitor the plurality of PDCCHs. PDCCHs are transmitted as anaggregate of one or several contiguous control channel elements (CCEs).The CCE is a logical allocation unit used to provide the PDCCHs at acoding rate based on the state of a radio channel The CCE corresponds toa plurality of resource element groups. The format of the PDCCH and thenumber of available bits are determined based on a correlation betweenthe number of CCEs and the coding rate provided by the CCEs. The eNB (orbase station) determines a PDCCH format according to a DCI to betransmitted to the UE, and attaches a Cyclic Redundancy Check (CRC) tocontrol information. The CRC is masked with a Radio Network TemporaryIdentifier (RNTI) according to an owner or usage of the PDCCH. If thePDCCH is for a specific UE, a cell-RNTI (C-RNTI) of the UE may be maskedto the CRC. Alternatively, if the PDCCH is for a paging message, apaging indicator identifier P-RNTI) may be masked to the CRC. If thePDCCH is for system information (more specifically, a system informationblock (SIB)), a system information identifier and a system informationRNTI (SI-RNTI) may be masked to the CRC. To indicate a random accessresponse that is a response for transmission of a random access preambleof the UE, a random access-RNTI (RA-RNTI) may be masked to the CRC.

FIG. 4 is a diagram showing the structure of an uplink frame. The uplinksubframe may be divided into a control region and a data region in afrequency domain. A Physical Uplink Control Channel (PUCCH) includinguplink control information is allocated to the control region. APhysical Uplink Shared Channel (PUSCH) including user data is allocatedto the data region. In order to maintain single carrier characteristics,one UE does not simultaneously transmit the PUCCH and the PUSCH. ThePUCCH for one UE is allocated to an RB pair in a subframe. RBs belongingto the RB pair occupy different subcarriers with respect to two slots.Thus, the RB pair allocated to the PUCCH is “frequency-hopped” at a slotedge.

DCI Format

DCI formats 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3, 3A and 4 are definedin LTE-A (release 10). DCI formats 0, 1A, 3 and 3A have the same messagesize to reduce the number of blind decoding operations, which will bedescribed later. The DCI formats may be divided into i) DCI formats 0and 4 used for uplink scheduling grant, ii) DCI formats 1, 1A, 1B, 1C,2, 2A, 2B and 2C used for downlink scheduling allocation, and iii) DCIformats 3 and 3A for power control commands according to purpose ofcontrol information to be transmitted.

DCI format 0 used for uplink scheduling grant may include a carrierindicator necessary for carrier aggregation which will be describedlater, an offset (flag for format 0/format 1A differentiation) used todifferentiate DCI formats 0 and 1A from each other, a frequency hoppingflag that indicates whether frequency hopping is used for uplink PUSCHtransmission, information about resource block assignment, used for a UEto transmit a PUSCH, a modulation and coding scheme, a new dataindicator used to empty a buffer for initial transmission with respectto an HARQ process, a transmit power control (TPC) command for ascheduled PUSCH, information on a cyclic shift for a demodulationreference signal (DMRS) and OCC index, and an uplink index and channelquality indicator request necessary for a TDD operation, etc. DCI format0 does not include a redundancy version, differently from DCI formatsrelating to downlink scheduling allocation, because DCI format 0 usessynchronous HARQ. The carrier offset is not included in DCI formats whencross-carrier scheduling is not used.

DCI format 4 is newly added to DCI formats in LTE-A release 10 andsupports application of spatial multiplexing to uplink transmission inLTE-A. DCI format 4 has a larger message size because it furtherincludes information for spatial multiplexing. DCI format 4 includesadditional control information in addition to control informationincluded in DCI format 0. DCI format 4 includes information on amodulation and coding scheme for the second transmission block,precoding information for multi-antenna transmission, and soundingreference signal (SRS) request information. DCI format 4 does notinclude the offset for format 0/format 1A differentiation because it hasa size larger than DCI format 0.

DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink schedulingallocation may be divided into DCI formats 1, 1A, 1B, 1C and 1D that donot support spatial multiplexing and DCI formats 2, 2A, 2B and 2C thatsupport spatial multiplexing.

DCI format 1C supports only frequency contiguous allocation as compactfrequency allocation and does not include the carrier indicator andredundancy version, compared to other formats.

DCI format 1A is for downlink scheduling and random access procedure.DCI format 1A may include a carrier indicator, an indicator thatindicates whether downlink distributed transmission is used, PDSCHresource allocation information, a modulation and coding scheme, aredundancy version, a HARQ processor number for indicating a processorused for soft combining, a new data indicator used to empty a buffer forinitial transmission with respect to a HARQ process, a TPC command for aPUCCH, an uplink index necessary for a TDD operation, etc.

DCI format 1 includes control information similar to that of DCI format1A. DCI format 1 supports non-contiguous resource allocation whereas DCIformat 1A supports contiguous resource allocation. Accordingly, DCIformat 1 further includes a resource allocation header, and thusslightly increases control signaling overhead as a trade-off for anincrease in resource allocation flexibility.

Both DCI formats 1B and 1D further include precoding information,compared to DCI format 1. DCI format 1B includes PMI acknowledgement andDCI format 1D includes downlink power offset information. Most controlinformation included in DCI formats 1B and 1D corresponds to that of DCIformat 1A.

DCI formats 2, 2A, 2B and 2C include most control information includedin DCI format 1A and further include information for spatialmultiplexing. The information for spatial multiplexing includes amodulation and coding scheme for the second transmission block, a newdata indicator, and a redundancy version.

DCI format 2 supports closed loop spatial multiplexing and DCI format 2Asupports open loop spatial multiplexing. Both DCI formats 2 and 2Ainclude precoding information. DCI format 2B supports dual layer spatialmultiplexing combined with beamforming and further includes cyclic shiftinformation for a DMRS. DCI format 2C may be regarded as an extendedversion of DCI format 2B and supports spatial multiplexing for up to 8layers.

DCI formats 3 and 3A may be used to complement the TPC informationincluded in the aforementioned DCI formats for uplink scheduling grantand downlink scheduling allocation, that is, to support semi-persistentscheduling. A 1-bit command is used per UE in the case of DCI format 3whereas a 2-bit command is used per UE in the case of DCI format 3A.

One of the above-mentioned DCI formats is transmitted through a PDCCH,and a plurality of PDCCHs may be transmitted in a control region. A UEcan monitor the plurality of PDCCHs.

Downlink Control Channel Structure

The first three OFDM symbols for each subframe can be basically used asa transmission region of a downlink control channel, and the first tothird OFDM symbols may be used according to overhead of a downlinkcontrol channel. PCFICH may be used to adjust the number of OFDM symbolsfor a downlink control channel per subframe. In order to provideacknowledgement/negative acknowledgment (ACK/NACK) information foruplink transmission on downlink, a Physical Hybrid-automatic repeatrequest (ARQ) Indicator Channel (PHICH) may be used. In addition, aPDCCH may be used to transmit either control information for downlinkdata transmission or control information for uplink data transmission.

FIGS. 5 and 6 exemplarily show that the above-mentioned downlink controlchannels are allocated in units of a resource element group (REG) in acontrol region for each subframe. In more detail, FIG. 5 shows a systemhaving 1Tx antenna or 2Tx antennas, and FIG. 6 shows a system having 4Txantennas. As can be seen from FIGS. 5 and 6, an REG serving as a basicresource unit to which a control channel is allocated is composed of 4concatenated resource elements (REs) in a frequency domain other thansome REs to which reference signals are allocated. A predeterminednumber of REGs may be used to transmit a downlink control channelaccording to downlink control channel (DCH) overhead.

PCFICH (Physical Control Format Indicator Channel)

In order to provide resource allocation information or the like of thecorresponding subframe to each subframe, a PDCCH may be transmittedamong OFDM symbol indices #0 to #2. In accordance with overhead of acontrol channel, an OFDM symbol index #0 may be used, OFDM symbolindices #0 and #1 may be used, or OFDM symbol indices #0 to #2 may beused. The number of OFDM symbols used by a control channel may bechanged per subframe, and information regarding the number of OFDMsymbols may be provided over a PCFICH. Therefore, PCFICH must betransmitted per subframe.

Three kinds of information can be provided through a PCFICH. Thefollowing Table 1 shows a Control Format Indicator of a PCFICH. CFI=1denotes that a PDCCH is transmitted at OFDM symbol index #0, CFI=2denotes that a PDCCH is transmitted at OFDM symbol indices #0 and #1,and CFI=3 denotes that a PDCCH is transmitted at OFDM symbol indices #0to #2.

TABLE 1 CFI CFI codeword <b₀, b₁, . . . , b₃₁> 1 <0, 1, 1, 0, 1, 1, 0,1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0,1> 2 <1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1,0, 1, 1, 0, 1, 1, 0, 1, 1, 0> 3 <1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1,1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1> 4 <0, 0, 0, 0,0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, (Reserved) 0,0, 0, 0, 0, 0, 0, 0, 0>

Information transmitted over a PCFICH may be differently definedaccording to system bandwidth. For example, if a system bandwidth isless than a specific threshold value, CFI=1, CFI=2, and CFI=3 mayindicate that two OFDM symbols, three OFDM symbols, and four OFDMsymbols are used for a PDCCH, respectively.

FIG. 7 is a conceptual diagram illustrating a PCFICH transmissionscheme. An REG shown in FIG. 7 may be composed of 4 subcarriers, and maybe composed only of data subcarriers other than a reference signal (RS).Generally, a transmit diversity scheme may be applied to the REG. Toprevent inter-cell interference of the PCFICH, the REGs to which thePCFICH is mapped may be shifted per cell in the frequency domain(according to a cell ID). The PCFICH is transmitted at the first OFDMsymbol of a subframe all the time. Accordingly, when receiving asubframe, the receiver first confirms PCFICH information, and recognizesthe number of OFDM symbols needed for PDCCH transmission, such that itcan receive control information transmitted over a PDCCH.

Physical Hybrid-ARQ Indicator Channel (PHICH)

FIG. 8 shows the positions of PCFICH and PHICH generally applied to aspecific bandwidth. ACK/NACK information for uplink data transmission istransmitted over a PHICH. A plurality of PHICH groups is constructed ina single subframe, and a plurality of PHICHs may be present in a singlePHICH group. Therefore, PHICH channels for multiple UEs are contained ina single PHICH group.

Referring to FIG. 8, allocating a PHICH to each UE of a plurality ofPHICH groups is achieved not only using a lowest physical resource block(PRB) index of a PUSCH resource allocation but also a cyclic shift (CS)index for a demodulation RS (DMRS) transmitted on a UL grant PDCCH. DMRSis an uplink reference signal, and is provided along with ULtransmission so as to perform channel estimation for demodulating ULdata. In addition, a PHICH resource is signaled as an index pair such as(n_(PHICH) ^(group), n_(PHICH) ^(seq)). In the index pair (n_(PHICH)^(group), n_(PHICH) ^(seq)), n_(PHICH) ^(group) denotes a PHICH groupnumber and n_(PHICH) ^(seq) denotes an orthogonal sequence index in thecorresponding PHICH group. n_(PHICH) ^(group) and n_(PHICH) ^(seq) aredefined as shown in the following equation 1.

n _(PHICH) ^(group)=(I _(PRB) _(_) _(RA) ^(lowest) ^(_) ^(index) +n_(DMRS))mod N _(PHICH) ^(group)

n _(PHICH) ^(seq)=(└I _(PRB) _(_) _(RA) ^(lowest) ^(_) ^(index) /N_(PHICH) ^(group) ┘+n _(DMRS))mod 2N _(SF) ^(PHICH)  [Equation 1]

In Equation 1, n_(DMRS) denotes a cyclic shift of a DMRS used for uplinktransmission related to a PHICH, and is mapped to a value of ‘cycleshift for DMRS’ field of the latest UL grant control information (e.g.,DCI format 0 or 4) for a transport block (TB) associated with thecorresponding PUSCH transmission. For example, the ‘cyclic shift forDMRS’ field of the latest UL grant DCI format may be 3 bits long. If the‘cyclic shift for DMRS’ field is set to “000”,n_(DMRS) may be set tozero ‘0’.

In Equation 1, N_(SF) ^(PHICH) denotes the size of a spreading factorused for PHICH modulation. I_(PRB) _(_) _(RA) ^(lowest) ^(_) ^(index) isthe lowest PRB index of a first slot of the corresponding PUSCHtransmission. I_(PHICH) is set to the value of 1 only when the TDDsystem is in a special case (if UL/DL configuration is set to zero ‘0’and PUSCH transmission is achieved at subframe n=4 or n=9, and I_(PHICH)is set to zero ‘0’ in the remaining cases other than the special case.N_(PHICH) ^(group) denotes the number of PHICH groups configured by ahigher layer. N_(PHICH) ^(group) can be obtained using the followingequation 2.

$\begin{matrix}{N_{PHICH}^{group} = \left\{ \begin{matrix}\left\lceil {N_{g}\left( {N_{RB}^{DL}/8} \right)} \right\rceil & {{for}\mspace{14mu} {normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}} \\{2 \cdot \left\lceil {N_{g}\left( {N_{RB}^{DL}/8} \right)} \right\rceil} & {{for}\mspace{14mu} {extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In Equation 2, N_(g) denotes information regarding the amount of PHICHresources transmitted on a physical broadcast channel (PBCH), and N_(g)is 2 bits long and is denoted by N_(g)∈{⅙, ½, 1,2}. In Equation 2,N_(RB) ^(DL) denotes the number of resource blocks (RBs) configured indownlink.

In addition, examples of orthogonal sequences defined in the legacy 3GPP

LTE Release 8/9 are shown in the following table 2.

TABLE 2 Orthogonal sequence Sequence index Normal cyclic prefix Extendedcyclic prefix n_(PHICH) ^(seq) N_(SF) ^(PHICH) = 4 N_(SF) ^(PHICH) = 2 0[+1 +1 +1 +1] [+1 +1] 1 [+1 −1 +1 −1] [+1 −1] 2 [+1 +1 −1 −1] [+j +j] 3[+1 −1 −1 +1] [+j −j] 4 [+j +j +j +j] — 5 [+j −j +j −j] — 6 [+j +j −j−j] — 7 [+j −j −j +j] —

FIG. 9 shows a downlink resource element position mapped to a PHICHgroup. A PHICH group may be constructed in different time domains (i.e.,different OFDM Symbols (OSs)) of a single subframe shown in FIG. 9according to a PHICH duration.

PDCCH Processing

When PDCCHs are mapped to REs, control channel elements (CCEs)corresponding to contiguous logical allocation units are used. A CCEincludes a plurality of (e.g. 9) REGs and an REG includes 4 neighboringREs except for a reference signal (RS).

The number of CCEs necessary for a specific PDCCH depends on a DCIpayload corresponding to control information size, cell bandwidth,channel coding rate, etc. Specifically, the number of CCEs for aspecific PDCCH can be determined based on PDCCH format shown in Table 3.

TABLE 3 PDCCH Number of Number of Number of format CCEs REGs PDCCH bits0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

While one of the above-mentioned four PDCCH formats may be used, this isnot signaled to a UE. Accordingly, the UE performs decoding withoutknowing the PDCCH format, which is referred to as blind decoding. Sinceoperation overhead is generated if a UE decodes all CCEs that can beused for downlink for each PDCCH, a search space is defined inconsideration of limitation for a scheduler and the number of decodingattempts.

The search space is a set of candidate PDCCHs composed of CCEs on whicha UE needs to attempt to perform decoding at an aggregation level. Theaggregation level and the number of candidate PDCCHs can be defined asshown in Table 4.

TABLE 4 The number of Search space PDCCH Aggregation level Size (CCEunit) candidates UE- 1 6 6 specific 2 12 6 4 8 2 8 16 2 Common 4 16 4 816 2

As shown Table 4, the UE has a plurality of search spaces at eachaggregation level because 4 aggregation levels are present. The searchspaces may be divided into a UE-specific search space and a commonsearch space, as shown in Table 4. The UE-specific search space is for aspecific UE. Each UE may check an RNTI and CRC which mask a PDCCH bymonitoring a UE-specific search space thereof (attempting to decode aPDCCH candidate set according to an available DCI format) and acquirecontrol information when the RNTI and CRC are valid.

The common search space is used for a case in which a plurality of UEsor all UEs need to receive PDCCHs, for system information dynamicscheduling or paging messages, for example. The common search space maybe used for a specific UE for resource management. Furthermore, thecommon search space may overlap with the UE-specific search space.

The search space may be decided by the following equation 3.

L·{(Y_(k)+m′)mod└N_(CCE,k)/L┘}+i  [Equation 3]

In Equation 3, L is an aggregation level, Y_(k) is a variable decided byRNTI and subframe number (k), m′ is the number of PDCCH candidates. Ifcarrier aggregation (CA) is used, m′ is denoted by m′=m+M^((L))·n_(CI).If CA is not used, m′ is denoted by m′=m, where m=0, . . . , M^((L))−1.M^((L)) is the number of PDCCH candidates. N_(CCE,k) is a total numberof CCEs of a control region at the k-th subframe. i is an index fordetermination of a separate CCE in each PDCCH candidate in the PDCCH andsatisfies i=0, . . . , L−1. In a common search space, Y_(k) is alwaysset to zero ‘0’.

FIG. 10 is a conceptual diagram illustrating a UE-specific search space(shaded part) in each aggregation level defined by Equation 3. In FIG.10, it should be noted that carrier aggregation (CA) is not used and thenumber of N_(CCE,k) is exemplarily set to 32.

FIGS. 10(a), 10(b), 10(c), and 10(d) show a case of an aggregation level‘1’, a case of an aggregation level ‘2’, a case of an aggregation level‘4’, and a case of an aggregation level ‘8’, respectively. In FIG. 10, astart CCE of a search space in each aggregation level is determined tobe an RNTI and subframe number (k), and may have different valuesaccording to individual aggregation levels due to a modulo function andan aggregation level (L) within the same subframe for one UE. The startCCE may always be set only to a multiple of an aggregation level due tothe aggregation level (L). In this case, it is premised that Y_(k) isset to, for example, a CCE number #18. The UE attempts to sequentiallyperform decoding from the beginning of a start CCE in units of CCEsdecided by the corresponding aggregation level. For example, as can beseen from FIG. 10(b), the UE attempts to perform decoding on the basisof two CCEs according to an aggregation level from the beginning of aCCE number #4 acting as a start CCE.

The UE attempts to decode a search space, as described above. The numberof decoding attempts is determined by DCI format and transmission modedetermined through RRC signaling. When carrier aggregation (CA) is notapplied, the UE needs to perform a maximum of 12 decoding attemptsbecause 2 DCI sizes (DCI format 0/1A/3/3A and DCI format 1C) have to beconsidered for each of 6 PDCCH candidates for a common search space. Fora UE-specific search space, 2 DCI sizes are considered for (6+6+2+2=16)PDCCH candidates and thus a maximum of 32 decoding attempts is needed.Accordingly, a maximum of 44 decoding attempts needs to be performedwhen carrier aggregation (CA) is not applied.

On the other hand, if carrier aggregation (CA) is used, as manyUE-specific search space as the number of DL resources (componentcarriers: CCs) and a decoding process for DCI format 4 are furtheradded, such that a maximum number of decoding times can be increasedmore and more.

Reference Signal (RS)

In a wireless communication system, since packets are transmittedthrough a radio channel, a signal may be distorted during transmission.In order to enable a reception side to correctly receive the distortedsignal, distortion of the received signal should be corrected usingchannel information. In order to detect the channel information, amethod of transmitting a signal, of which both the transmission side andthe reception side are aware, and detecting channel information using adistortion degree when the signal is received through a channel ismainly used. The above signal is referred to as a pilot signal or areference signal (RS).

When transmitting and receiving data using multiple antennas, thechannel states between the transmission antennas and the receptionantennas should be detected in order to correctly receive the signal.Accordingly, each transmission antenna has an individual RS. In moredetail, an independent RS should be transmitted through each Tx port.

RSs may be divided into downlink RSs and uplink RSs. In the current LTEsystem, the uplink RSs include:

i) DeModulation-Reference Signal (DM-RS) used for channel estimation forcoherent demodulation of information delivered on a PUSCH and a PUCCH;and

ii) Sounding Reference Signal (SRS) used for a BS (eNB) or a network tomeasure the quality of an uplink channel in a different frequency.

The downlink RSs are categorized into:

i) Cell-specific Reference Signal (CRS) shared among all UEs of a cell;

ii) UE-specific RS dedicated to a specific UE;

iii) DM-RS used for coherent demodulation of a PDSCH, when the PDSCH istransmitted;

iv) Channel State Information-Reference Signal (CSI-RS) carrying CSI,when downlink DM-RSs are transmitted;

v) Multimedia Broadcast Single Frequency Network (MBSFN) RS used forcoherent demodulation of a signal transmitted in MBSFN mode; and

vi) positioning RS used to estimate geographical position informationabout a UE (i.e., to geolocate a UE).

RSs may also be divided into two types according to their purposes: RSfor channel information acquisition and RS for data demodulation. Sinceits purpose lies in that a UE acquires downlink channel information, theformer should be transmitted in a broad band and received even by a UEthat does not receive downlink data in a specific subframe. This RS isalso used in situations such as handover. The latter is an RS that a BS(eNB) transmits along with downlink data in specific resources. A UE candemodulate the data by measuring a channel using the RS. This RS shouldbe transmitted in a data transmission area.

CRSs serve two purposes, namely, channel information acquisition anddata demodulation. A UE-specific RS is used only for data demodulation.CRSs are transmitted in every subframe in a broad band and CRSs for upto four antenna ports are transmitted according to the number of Txantennas in an eNB.

For example, if the BS (eNB) has two Tx antennas, CRSs for antenna ports0 and 1 are transmitted. In the case of four Tx antennas, CRSs forantenna ports 0 to 3 are respectively transmitted.

FIG. 11(a) shows a pattern within one RB for Antenna Port #0. FIG. 11(b)shows a CRS pattern within one RB when there are four Tx antennas of aBS or eNB.

Referring to FIGS. 11(a) and 11(b), when CRS is mapped to time-frequencyresources, a reference signal (RS) for one antenna port on a frequencyaxis is mapped to one RE per 6 REs, and is then transmitted. One RB iscomposed of 12 REs on a frequency axis, such that 2 REs are used per RBin case of an RE for one antenna port.

CSI-RS

MIMO schemes are classified into an open-loop MIMO scheme and aclosed-loop MIMO scheme. The open-loop MIMO scheme means that atransmitter performs MIMO transmission without receiving CSI feedbackinformation from a MIMO receiver. The closed-loop MIMO scheme means thata transmitter receives CSI feedback information from the MIMO receiverand performs MIMO transmission. In accordance with the closed-loop MIMOscheme, each of a transmitter and a receiver can perform beamforming onthe basis of CSI so as to obtain a multiplexing gain of a MIMOtransmission antenna. The transmitter (for example, BS) can allocate anuplink control channel or an uplink shared channel to a receiver (forexample, a user equipment) in such a manner that the receiver can feedback the CSI.

The feedback CSI may include a rank indicator (RI), a precoding matrixindex (PMI), and a channel quality indicator (CQI).

RI is information on a channel rank. The channel rank means a maximumnumber of layers (or streams) via which different information can betransmitted through the same time-frequency resources. Since a rankvalue is determined depending on long-term fading of a channel, the rankvalue is generally fed back for a longer period than PMI and CQI. Thatis, the rank value can be fed back less frequently than PMI and CQI.

PMI is information regarding a precoding matrix used for datatransmission from the transmitter, and includes spatial characteristicsof a channel. Precoding means that a transmit layer is mapped to atransmit antenna, and the layer-antenna mapping relationship can bedetermined by precoding matrices. PMI corresponds to a UE-preferredprecoding matrix index of a BS on the basis of metric data such asSignal-to-Interference plus Noise Ratio (SINR). In order to reducefeedback overhead of the precoding information, a transmitter and areceiver may share a variety of precoding matrices in advance, and onlyindices indicating a specific precoding matrix from among thecorresponding codebook can be fed back.

CQI is information indicating channel quality or channel strength. CQImay be represented by a combination of predetermined MCSs. That is, afeedback CQI index may indicate a modulation scheme and a code rate.Generally, a reception SINR capable of being obtained when the BSconstructs a spatial channel using a PMI is applied to CQI.

PSS (Primary Synchronous Signal)/SSS (Secondary Synchronous Signal)

FIG. 12 is a conceptual diagram illustrating PSS and SSS acting assynchronous signals used in cell search in LTE/LTE-A system. Prior todescribing PSS and SSS, the cell search will hereinafter be described.In more detail, if a UE initially connects to a cell, the cell search iscarried out to perform handover from a current connection cell toanother cell or to perform cell reselection. The cell search may beachieved by frequency and symbol synchronization acquisition of thecell, downlink frame synchronous acquisition of the cell, and cell-IDdecision. Three cell IDs may construct one cell group, and 168 cellgroups may be present.

For cell search, the BS (or eNB) transmits PSS and SSS. The UE candetect the PSS so as to acquire 5 ms timing of the cell, and canrecognize the cell ID contained in the cell group. In addition, the UEdetects the SSS so that the UE can recognize radio frame timing and acell group.

Referring to FIG. 12, PSS is transmitted at subframes #0 and #5. Moreparticularly, the PSS is transmitted to the last OFDM symbol of a firstslot at subframes #0 and #5. In addition, SSS is transmitted from asecond OFDM symbol of the last end of the first slot of the subframes #0and #5. That is, SSS is transmitted from an OFDM symbol just before PSStransmission. This transmission time relates to the case of FDD.

In case of TDD (not shown), PSS is transmitted at a third symbol (i.e.,DwPTS) of subframes #1 and #6. SSS is transmitted at the last symbol ofsubframes #0 and #5. That is, in TDD, SSS is transmitted earlier thanPSS by three symbols.

PSS is a Zadoff-Chu sequence having the length of 63. In actualtransmission, zero ‘0’ is padded to both ends of a sequence, and thesequence is transmitted to 73 subcarriers (72 subcarriers other than DCsubcarriers, i.e., 6RBs) of the center part of the system frequencybandwidth. SSS is composed of 62 sequences having the length of 62formed when two sequences each having the length of 31 arefrequency-interleaved. In the same manner as in PSS, SSS is transmittedon 72 subcarriers located at the center part of the entire systembandwidth.

Physical Broadcast Channel (PBCH)

FIG. 13 is a conceptual diagram illustrating a PBCH. PBCH is used fortransmission of a master information block (MIB). By means of the PBCH,a user equipment (UE) acquires synchronization through the abovedescribed PSS/SSS, obtains a cell ID, and obtains the next systeminformation. In this case, MIB may include DL cell bandwidthinformation, PHICH configuration information, a system frame number(SFN), etc.

Referring to FIG. 13, one BCH transport block (TB) is transmittedthrough a first subframe from among four continuous radio frames. Inmore detail, BCH is transmitted at first four OFDM symbols of a secondslot of Subframe #0 in the four contiguous radio frames, and istransmitted on the center 72 subcarriers of the entire bandwidth on afrequency axis. This means 6RBs indicating the smallest DL bandwidth.Although the UE does not recognize the size of a total system bandwidth,the UE can decode the BCH without any problems.

The above-mentioned PSS/SSS and PBCH transmission time points for use inFDD will hereinafter be described with reference to FIG. 14. Referringto FIG. 14, in each radio frame, SSS and PSS are transmitted at the lasttwo OFDM symbols of a first slot of a subframe #0, and PBCH is thentransmitted at initial four OFDM symbols of the second slot. Inaddition, SSS and PSS are respectively transmitted at the last two OFDMsymbols of the first slot of a subframe #5. Since PDCCH is transmittedon a control region (initial one to four OFDM symbols of each subframeaccording to a cell bandwidth) indicated by PCFICH, PDCCH is separatedfrom a resource region in which PSS/SSS and PBCH are transmitted. Inaddition, PDCCH is not transmitted at a transmission position of CRS andCSI-RS. However, in case of e-PDCCH transmission, an unexpectedcollision may occur in the relationship between PSS/SSS and PBCH,resulting in the occurrence of problems.

e-PDCCH will hereinafter be described in detail. e-PDCCH indicates thatPDCCH is transmitted from the legacy LTE/LTE-A system to a data region(i.e., a resource region for use in PUSCH transmission). e-PDCCH hasbeen introduced due to the legacy PDCCH capacity limitation,interference between PDCCHs of the cells, and/or interference betweenPDCCH and PUSCH/PUCCH of the cells in carrier aggregation (CA),Coordinated Multi Point (COMP), Multi User Multiple Input MultipleOutput (MU-MIMO), Machine Type Communication (MTC), HeterogeneousNetwork (HetNet), etc. e-PDCCH may be transmitted in a PDSCH region asdescribed above, and may also be transmitted on the basis of ademodulation reference signal (DMRS). That is, when the UE decodese-PDCCH, channel estimation may be used for DMRS. For this purpose, theBS or eNB may perform precoding of e-PDCCH and DMRS.

In other words, e-PDCCH may be transmitted in the PDSCH region. In thiscase, e-PDCCH may collide with a resource region to which basicinformation for the system, PS S/SSS , PBCH, RS, CSI-RS, etc. istransmitted.

Accordingly, according to the embodiments of the present invention,e-PDCCH cannot be allocated/transmitted to 6 RBs located at the centerpart (to which PSS, SSS, and/or PBCH are transmitted.) of the entirefrequency band. From the viewpoint of a UE, it is expected that e-PDCCHis not transmitted, and e-PDCCH decoding/blind decoding is not performedin the corresponding region. In addition, if PSS, SSS, and PBCH aretransmitted during e-PDCCH transmission, the embodiments of the presentinvention perform e-PDCCH puncturing at an RE where e-PDCCH overlapswith the above signals. In addition, if PSS, SSS, PBCH are transmittedduring e-PDCCH transmission, the embodiments do not transmit e-PDCCH atthe RE where e-PDCCH overlaps with the above signals, and perform ratematching.

Detailed embodiments of the present invention will hereinafter bedescribed in detail. In the following description, if e-PDCCH is notallocated/transmitted to a specific region, it can be appreciated thatthe UE assumes/expects that e-PDCCH is not transmitted to a specificregion and e-PDCCH decoding/blind decoding is performed in a resourceregion other than the specific region.

EMBODIMENT 1

In a frequency domain (i.e., 6 RBs located at the center part of theentire frequency band) to which PSS/SSS and/or PBCH are transmitted in asubframe in which PSS/SSS and/or PBCH are transmitted, e-PDCCH may notbe allocated/transmitted. In other words, in the subframe in whichPSS/SSS and/or PBCH are transmitted, e-PDCCH may not beallocated/transmitted at a PRB pair to which PSS/SSS and/or PBCH areallocated. That is, the resource region to which e-PDCCH is allocateddoes not correspond to resources (PRB pair corresponding to 6 RBslocated at the center part of the entire frequency band) used fortransmission of synchronous signals (PSS/SSS) or PBCH.

The above-mentioned embodiment in case of FDD will hereinafter bedescribed with reference to FIG. 15. FIG. 15(a) shows a subframe #5 towhich PSS/SSS is transmitted, and FIG. 15(b) shows a subframe #0 towhich PSS/SSS and PBCH are transmitted. In FIG. 15(a), e-PDCCH is nottransmitted to a frequency region 1510 to which PSS/SSS is transmitted.In FIG. 15(b), e-PDCCH is not transmitted to a frequency domain 1520 towhich PSS/SSS and/or PBCH are transmitted.

Although not shown in FIGS. 15(a) and 15(b), from the viewpoint of TDD,e-PDCCH may not be transmitted to a frequency domain (corresponding to 6RBs located at the center part of the entire frequency band) to whichPSS/SSS and/or PBCH are transmitted not only at Subframes #0 and #5 towhich PSS is transmitted, but also at Subframes #1 and #6 to which SSSis transmitted.

EMBODIMENT 2

PSS/SS is transmitted only to a first slot in case of FDD. e-PDCCH isnot allocated/transmitted to a first slot in a subframe to which PSS/SSSis transmitted, and e-PDCCH can be allocated/transmitted to a secondslot. In addition, e-PDCCH may not be allocated/transmitted to first andsecond slots in a subframe to which PSS/SSS and PBCH are transmitted. Inmore detail, e-PDCCH may not be allocated/transmitted to 6 RBs locatedat the center part of the first slot at Subframe #5 to which PSS/SSS istransmitted. e-PDCCH may not be allocated/transmitted to 6 RBs locatedat the center part of the first and second slots at Subframe #0 to whichPSS/SSS and PBCH are transmitted, as shown in FIG. 16. It can berecognized that e-PDCCH is not allocated/transmitted not only to 6 RBs(1610) located at the center part of a first slot shown in FIG. 16(a)showing a subframe #5, but also to 6 RBs (1620) located at the centerpart of the first and second slots.

In brief, a resource region in which the UE performs decoding fore-PDCCH may be changed according to a combination of transmission andnon-transmission of PSS, SSS and PBCH in a specific subframe. In otherwords, the UE does not transmit e-PDCCH to a resource regioncorresponding to 72 subcarriers (i.e., 6 RBs) located at the center partof the entire system bandwidth at Subframe #0 to which PSS, SSS and PBCHare transmitted. The UE estimates that e-PDCCH is not transmitted to afirst slot at Subframe #5 to which PSS and SSS are transmitted, suchthat the UE can perform decoding at the subframe #5.

Alternatively, the UE estimates that e-PDCCH is not transmitted usingOFDM symbols used for transmission of PSS, SSS and PBCH, and may performdecoding according to the estimated result. In more detail, the UE mayestimate that e-PDCCH is not transmitted at the 6^(th) and 7^(th) OFDMsymbols of the subframe #5 to which a synchronous signal is transmitted,and may also estimate that e-PDCCH is not transmitted at 6^(th) to11^(th) OFDM symbols of the subframe #0 to which a synchronous signaland system information are transmitted.

In another example, the UE may estimate that e-PDCCH is not transmittedto a resource region to which PSS, SSS and/or PBCH are transmitted atthe subframes #0 and #5, and may perform decoding in the resourceregion. That is, the UE may estimate that e-PDCCH is not transmitted notonly to a resource region corresponding to 6 RBs located at the centerpart of the 6^(th) to 7^(th) OFDM symbols of the subframe #5, but alsoto a resource region corresponding to 6 RBs located at the center partof the 6^(th) to 11^(th) OFDM symbols of the subframe #0.

EMBODIMENT 3

In case of TDD, since a synchronous signal can be transmitted at thefirst and second slots, e-PDCCH may not be allocated/transmitted to 6RBs located at the center part of the frequency domain at OFDM symbolsused for PSS/SS transmission. In addition, e-PDCCH may be transmitted tothe remaining OFDM symbols other than OFDM symbols used for PSS/SSStransmission. In the subframe to which the synchronous signal and PBCHare transmitted, e-PDCCH may not be transmitted to 6 RBs located at thecenter part of the first and second slots as shown in theabove-mentioned embodiment.

In more detail, for example, in the case of using the extended CP, thesynchronous signal is transmitted not only at a third OFDM symbol of thefirst slot but also at a sixth OFDM symbol of the second slot, and PBCHmay be transmitted to the first to fourth OFDM symbols of the secondslot. In this case, e-PDCCH may be allocated through the remaining OFDMsymbols other than OFDM symbols used for PSS/SSS transmission. Inaddition, e-PDCCH may not be transmitted to 6 RBs located at the centerpart of the subframe to which PSS, SSS, and PBCH are transmitted.

As can be seen from the above-mentioned description, REs used fortransmission of RS or CSI-RS may be contained in the resource region inwhich the UE estimates non-transmission of e-PDCCH. For example, theabove-mentioned embodiment has disclosed that the remaining region otherthan a specific region corresponding to 72 subcarriers located at thecenter part is used for e-PDCCH transmission, and decoding should beperformed in the above remaining region. However, the scope or spirit ofthe present invention is not limited thereto, abd REs used for RS orCSI-RS transmission may be used as a UE-estimated region in which the UEestimates non-transmission of e-PDCCH.

In the meantime, the UE-estimated region in which the UE estimatesnon-transmission of e-PDCCH may be obtained when the BS or eNB performspuncturing or rate matching of REs belonging to the correspondingregion.

FIG. 17 is a block diagram illustrating a BS (eNB) device and a UEdevice according to the embodiments of the present invention.

Referring to FIG. 17, the BS device 1710 according to the presentinvention may include a reception (Rx) module 1711, a transmission (Tx)module 1712, a processor 1713, a memory 1714, and a plurality ofantennas 1715. The plurality of antennas 1715 indicates the BS devicefor supporting MIMO transmission and reception. The reception (Rx)module 1711 may receive a variety of signals, data and information on anuplink starting from the UE. The Tx module 1712 may transmit a varietyof signals, data and information on a downlink for the UE. The processor1713 may provide overall control to the transmission point apparatus1710. The processor 1713 may be configured to implement the embodimentsof the present invention.

The processor 1713 of the BS device 1710 processes information receivedat the BS device 1710 and transmission information to be transmittedexternally. The memory 1714 may store the processed information for apredetermined time. The memory 1714 may be replaced with a componentsuch as a buffer (not shown).

Referring to FIG. 17, the UE device 1720 may include an Rx module 1721,a Tx module 1722, a processor 1723, a memory 1724, and a plurality ofantennas 1725. The plurality of antennas 1725 indicates a UE apparatussupporting MIMO transmission and reception. The Rx module 1721 mayreceive downlink signals, data and information from the BS (eNB). The Txmodule 1722 may transmit uplink signals, data and information to the BS(eNB). The processor 1723 may provide overall control to the UEapparatus 1720. The processor 1723 may be configured to implement theembodiments of the present invention.

The processor 1723 of the UE apparatus 1720 processes informationreceived at the UE device 1720 and transmission information to betransmitted externally. The memory 1724 may store the processedinformation for a predetermined time. The memory 1724 may be replacedwith a component such as a buffer (not shown).

The specific configurations of the BS device and the UE device may beimplemented such that the various embodiments of the present inventionare performed independently or two or more embodiments of the presentinvention are performed simultaneously. Redundant matters will not bedescribed herein for clarity.

The description of the BS device 1710 shown in FIG. 17 may be applied tothe eNB (BS), or may also be applied to a relay node (RN) acting as a DLtransmission entity or UL reception entity without departing from thescope or spirit of the present invention. In addition, the descriptionof the UE apparatus 1720 may be applied to the UE, or may also beapplied to a relay node (RN) acting as a UL transmission entity or DLreception entity without departing from the scope or spirit of thepresent invention.

The above-described embodiments of the present invention can beimplemented by a variety of means, for example, hardware, firmware,software, or a combination thereof.

In the case of implementing the present invention by hardware, thepresent invention can be implemented with application specificintegrated circuits (ASICs), Digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), a processor, a controller, amicrocontroller, a microprocessor, etc.

If operations or functions of the present invention are implemented byfirmware or software, the present invention can be implemented in theform of a variety of formats, for example, modules, procedures,functions, etc. Software code may be stored in a memory to be driven bya processor. The memory may be located inside or outside of theprocessor, so that it can communicate with the aforementioned processorvia a variety of well-known parts.

The detailed description of the exemplary embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the exemplary embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. For example, those skilledin the art may use each construction described in the above embodimentsin combination with each other. Accordingly, the invention should not belimited to the specific embodiments described herein, but should beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above exemplary embodiments are therefore to beconstrued in all aspects as illustrative and not restrictive. The scopeof the invention should be determined by the appended claims and theirlegal equivalents, not by the above description, and all changes comingwithin the meaning and equivalency range of the appended claims areintended to be embraced therein. Also, it will be obvious to thoseskilled in the art that claims that are not explicitly cited in theappended claims may be presented in combination as an exemplaryembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

Although the embodiments of the present invention have been disclosed onthe basis of the 3GPP LTE mobile communication system, the embodimentscan be equally or equivalently applied to various wireless communicationsystems.

1. A method for receiving control information through enhanced physicaldownlink control channel (EPDCCH) at a user equipment (UE) in a wirelesscommunication system, the method comprising: performing blind decodingof one or more EPDCCH candidates; and receiving control informationthrough the one or more EPDCCH candidates; wherein when a specificEPDCCH candidate overlaps in frequency with a transmission of eitherphysical broadcast channel (PBCH) or primary or secondarysynchronization signal, the UE does not perform blind decoding of thespecific EPDCCH candidate.
 2. The method of claim 1, wherein a frequencydomain on which either the PBCH or primary or secondary synchronizationsignal is transmitted corresponds to 6 resource blocks (6 RBs) locatedat a center part of an entire frequency bandwidth.
 3. A method fortransmitting control information through enhanced physical downlinkcontrol channel (EPDCCH) at a base station (BS) in a wirelesscommunication system, the method comprising: transmitting controlinformation through one or more EPDCCH candidates; wherein when aspecific EPDCCH candidate overlaps in frequency with a transmission ofeither physical broadcast channel (PBCH) or primary or secondarysynchronization signal, the control information is not transmittedthrough the specific EPDCCH candidate.
 4. The method of claim 3, whereina frequency domain on which either the PBCH or primary or secondarysynchronization signal is transmitted corresponds to 6 resource blocks(6 RBs) located at a center part of an entire frequency bandwidth.
 5. Auser equipment (UE) device for use in a wireless communication system,the UE comprising: a reception module; and a processor configured tocontrol the reception module to: perform blind decoding of one or moreenhanced physical downlink control channel (EPDCCH) candidates, andreceive control information through the one or more EPDCCH candidates,wherein when a specific EPDCCH candidate overlaps in frequency with atransmission of either physical broadcast channel (PBCH) or primary orsecondary synchronization signal, the processor does not perform blinddecoding of the specific EPDCCH candidate.
 6. The UE of claim 5, whereina frequency domain on which either the PBCH or primary or secondarysynchronization signal is transmitted corresponds to 6 resource blocks(6 RBs) located at a center part of an entire frequency bandwidth.
 7. Abase station (BS) device for use in a wireless communication system, theBS comprising: a transmission module; and a processor configured tocontrol the transmission module to transmit control information throughone or more enhanced physical downlink control channel (EPDCCH)candidates; wherein when a specific EPDCCH candidate overlaps infrequency with a transmission of either physical broadcast channel(PBCH) or primary or secondary synchronization signal, the controlinformation is not transmitted through the specific EPDCCH candidate. 8.The BS of claim 7, wherein a frequency domain on which either the PBCHor primary or secondary synchronization signal is transmittedcorresponds to 6 resource blocks (6 RBs) located at a center part of anentire frequency bandwidth.